The present invention relates to firing mechanisms for air weapons and to air weapons incorporating such firing mechanisms.
Many air weapons use a system of stored energy in which a spring, typically either a metallic coil spring or a sealed gas charge as described in GB No. 2,084,704 B, is compressed and retained in a compressed condition by a trigger mechanism prior to firing. When the trigger is operated the spring is released and drives a piston along a cylinder, compressing the air ahead of it, forcing the air through a transfer port and then through a barrel, carrying a projectile, typically a pellet, ahead of it.
The piston and spring assembly (or assemblies in the case of opposed piston configurations) will usually weigh several hundred grammes and will travel at very high speed. The assembly therefore has a considerable amount of kinetic energy at the end of the firing stroke.
Ideally, all the kinetic energy would be transferred to the projectile but, in practice, this is extremely difficult to achieve.
Typically, in the process of coming to rest, the piston assembly will bounce off the end of the cylinder or off a layer of highly-compressed air between it and the end of the cylinder. This bouncing action not only consumes some of the kinetic energy but is a major source of disturbance to the air weapon as a whole and is thus a cause of inaccuracy.
This problem has been very widely recognised for a very long time and many attempts have been made to overcome piston bounce. GB No. 1,604,456 and GB 2,173,287A are examples of earlier work towards this end.